1. Field of Invention
This invention relates to temperature measurement and more particularly to providing an indication of a temperature within living tissue.
2. Description of the Prior Art
When a patient has a cancerous tumor, a surgical procedure is often employed to remove the tumor. However, the surgical procedure may cause a spread of cancer throughout the body of the patient. Therefore, a surgical procedure may be undesirable.
Since ancient times, medical practitioners have known that the patient may be successfully treated by raising the temperature of a tumor, a treatment generally referred to as hyperthermia. One form of hyperthermia is the elevation of the temperature of a large portion of the patient's body where the tumor is located. Accordingly, in the late 1960's, medical practitioners treated patients with tumors in their arms and legs by a profusion therethrough of hot blood. Additionally, patients with tumors in their bladders were treated by flushing the bladders with hot fluid. In 1974 Scottish medical practitioners immersed patients in hot wax. Other medical practitioners have elevated the body temperature of patients by infecting them with malaria. The tumor either shrinks or disappears at a temperature of 43.degree. C. However, elevation of the temperature of a large portion of the body to 42.5.degree. C. may cause death (37.degree. C. is usually referred to as a normal body temperature). Therefore, the elevation of the temperature of a large portion of the body has been only moderately successful.
Although the elevation of a large portion of the human body above a temperature of 42.5.degree. C. may cause death, local tissue of the human body including the tumor may safely withstand temperatures above 43.degree. C. Accordingly, another form of hyperthermia is the elevation of the temperature of the local tissue including the tumor, thereby raising the temperature of the tumor. An early practitioner, Hippocrates, (around 600 B.C.) attempted to raise the temperature of the tumor via conduction by applying red hot irons to the skin. Hippocrates found, and modern medical practitioners have learned, that when the tumor is two centimeters beneath the skin, for example, heating the tumor to about 43.degree. C. via conduction may cause either severe burns or death.
American medical practitioners have used microwave radiation to elevate the temperature of the tissue including the tumor. The microwave radiation may be controlled to rapidly elevate the temperature of a known volume of tissue that extends from the surface of the skin to a known depth beneath the skin. While microwave radiation is used, it is desirable to prevent an over heating that may damage the tissue including the tumor. Therefore, it is correspondingly desirable to provide an indication of the temperature of the tissue including the tumor. Heretofore, suitable apparatus for providing an indication of a temperature of a tissue beneath the skin has not been available in the art.